The present invention relates generally to devices and methods useful in capturing embolic material in blood vessels. More specifically, the devices and methods provide a vessel filtering system for temporary deployment in arteries such as the carotid arteries and the aorta, and veins such as the subclavian vein and the superior vena cava. The system also includes a guidewire for directing endovascular devices, e.g., atherectomy, stent-deployment, or angioplasty catheters, to a region of interest and a guiding catheter with fluid flushing capability to assist in filtering.
Treatment of thrombotic or atherosclerotic lesions in blood vessels using the endovascular approach has recently been proven to be an effective and reliable alternative to surgical intervention in selected patients. For example, directional atherectomy and percutaneous translumenal coronary angioplasty (PTCA) with or without stent deployment are useful in treating patients with coronary occlusion. Atherectomy physically removes plaque by cutting, pulverizing, or shaving in atherosclerotic arteries using a catheter-deliverable endarterectomy device. Angioplasty enlarges the lumenal diameter of a stenotic vessel by exerting mechanical force on the vascular walls. In addition to using the angioplasty, stenting, and/or atherectomy on the coronary vasculature, these endovascular techniques have also proven useful in treating other vascular lesions in, for example, carotid artery stenosis, peripheral arterial occlusive disease (especially the aorta, the iliac artery, and the femoral artery), renal artery stenosis caused by atherosclerosis or fibromuscular disease, superior vena cava syndrome, occlusion iliac vein thrombosis resistant to thrombolysis.
It is well recognized that one of the complications associated with endovascular techniques is the dislodgment of embolic materials generated during manipulation of the vessel, thereby causing occlusion of the narrower vessels downstream and ischemia or infarct of the organ which the vessel supplies. In 1995, Waksman et al. disclosed that distal embolization is common after directional atherectomy in coronary arteries and saphenous vein grafts. See Waksman et al., American Heart Journal 129(3): 430-5 (1995), incorporated herein by reference. This study found that distal embolization occurs in 28% (31 out of 111) of the patients undergoing atherectomy. In January 1999, Jordan, Jr. et al. disclosed that treatment of carotid stenosis using percutaneous angioplasty with stenting procedure is associated with more than eight times the rate of microemboli seen using carotid endarterectomy. See Jordan, Jr. et al. Cardiovascular surgery 7(1): 33-8 (1999), incorporated herein by reference. Microemboli, as detected by transcranial Doppler monitoring in this study, have been shown to be a potential cause of stroke. The embolic materials include calcium, intimal debris, atheromatous plaque, thrombi, and/or air.
There are a number of devices designed to provide blood filtering for entrapment of vascular emboli. The vast majority of these devices are designed for permanent placement in veins to prevent pulmonary embolism. A temporary venous filter device is disclosed in Bajaj, U.S. Pat. No. 5,053,008 (this and all other references cited herein are expressly incorporated by reference as if fully set forth in their entirety herein). The Bajaj device is an intracardiac catheter for temporary placement in the pulmonary trunk of a patient predisposed to pulmonary embolism due to, e.g., hip surgery, major trauma, major abdominal or pelvic surgery, or immobilization. The Bajaj device includes an umbrella made from meshwork which traps venous emboli before they reach the lungs. This device is designed for venous filtration and is not suitable for arterial use because of the hemodynamic differences between arteries and veins.
There are very few intravascular devices designed for arterial use. Arteries are much more flexible and elastic than veins and, in the arteries, blood flow is pulsatile with large pressure variations between systolic and diastolic flow. These pressure variations cause the artery walls to expand and contract. Blood flow rates in the arteries vary from about 1 to about 5 L/min. Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial filtering system, which includes a catheter with a strainer device at its distal end. This device is inserted into the vessel downstream from the treatment site and, after treatment, the strainer is collapsed around the entrapped emboli and removed from the body. The Ginsburg device could not withstand flow rates of 5 L/min. It is designed for only small arteries and therefore could not capture emboli destined for all parts of the body. Ing. Walter Hengst GmbH and Co, German Patent DE 34 17 738, also discloses another arterial filter having a folding linkage system which converts the filter from the collapsed to the expanded state.
Filters mounted to the distal end of guidewires have been proposed for intravascular blood filtration. A majority of these devices includes a filter which is attached to a guidewire and is mechanically actuated via struts or a pre-shaped basket which deploy in the vessel. These filters are typically mesh xe2x80x9cparachutesxe2x80x9d which are attached to the shaft of the wire at the distal end and to wire struts which extend outward in a radial direction on the proximal end. The radial struts open the proximal end of the filter to the wall of the vessel. Blood flowing through the vessel is forced through the mesh thereby capturing embolic material in the filter. A major disadvantage associated with these filter devices is that the filters generally rely on vascular blood flow to push debris into the filters. If blood flow in the vessel becomes restricted, the loosely attached embolic material may not be subjected to normal turbulent blood flow. The embolic particles may stay in the vessel proximal to the filter until the higher normal flow is re-established (i.e., when the filter is removed), thereby reducing the efficacy of the filtering devices.
Another means of removing embolic material utilizes temporary occlusion devices, such as balloon occlusion catheters and vascular clamps, to isolate a section of a vessel. After blood flow is isolated in the vessel, fluid or blood within the vessel is aspirated to remove embolic debris. One of the disadvantages associated with occlusion devices is that they require temporary cessation or reduction in distal perfusion that may affect oxygenation of distal organs. Shunts may be placed distal to the devices to maintain perfusion to distal organs. However, insertion of the shunts creates additional trauma to the vessel and may generate additional embolic material.
What is needed are simple and safe blood filtering devices which can be temporarily placed in the arteries and veins and can be used with endovascular instruments to effectively prevent distal embolization. Existing devices are inadequate for this purpose.
Fixed or mobile plaque present in the aorta can dislodge and cause renal infarct or ischemia to other organs. The build up of plaque in the carotid arteries also poses a risk of ischemic stroke by embolization and presents an additional threat of reducing blood flow by occluding the vessel lumen. Plaque present in the iliac and femoral arteries may cause ischemia of the lower extremities, either through distal embolization of atheromatous material or through in situ stenosis of the diseased blood vessel, i.e., narrowing of lumenal diameter. Atherectomy or angioplasty with or without stent deployment in these vessels prevents the above disease from occurring, but can also create these conditions unless the device is specially designed to capture embolic material dislodged during the procedure.
The present invention provides devices and methods for temporary placement of blood filtering capabilities in an artery or vein during endovascular procedures. More specifically, the invention provides a filter flush system which accommodates insertion of endovascular catheters for removing atherosclerotic plaques and/or thrombi and enlarging the lumenal diameter of a stenotic vessel. The filter system also provides means for maintaining distal perfusion during isolation of blood flow, and for pushing embolic debris into the filter during a low-flow state, thereby enhancing filtering capabilities.
In one embodiment, the filter flush system includes an expandable filter, e.g., a parachute, basket, or scroll, mounted on a distal end of a guidewire, and a large diameter catheter (such as a guiding catheter, angiographic catheter, introducer sheath, vessel dilators) having a lumen communicating with a proximal end and a port at its distal end. The distal end of the catheter is adapted for insertion into an artery or vein. The proximal end of the catheter may include a hemostatic valve. An expandable occluder, which may comprise an elastomeric balloon, is disposed about the distal end of the guiding catheter and communicates with an inflation lumen for providing isolation of blood flow in the vessel. The lumen of the catheter is adapted to receive the guidewire, which passes through the distal port. A proximal end of the guidewire will typically be operable from outside the proximal end of the catheter for manipulation of the guidewire independently of the catheter. The lumen of the catheter is also adapted to receive an endovascular device, e.g., an angioplasty, stent-deployment, or atherectomy catheter.
The endovascular catheters typically include a proximal end, a distal end and a lumen which receives the guidewire. An excising member, e.g., a cutting blade, abrasive member, wire cutter, jaws, claws, pincher, snare, etc., is included at the distal region of an atherectomy catheter. An expandable balloon is included at a distal region of an angioplasty catheter. An expandable stent is mounted at a distal region of a stent-deployment catheter. The atherectomy catheter may optionally further include means for intravascular imaging, e.g., an ultrasonic transducer. In certain embodiments, the angioplasty catheters include a stent disposed about the balloon at their distal region. Intravascular imaging devices and stents are fully described in the art and will not be further discussed here.
In another embodiment, the expandable filter comprises an expansion frame and a mesh disposed over the frame. In certain embodiments, the frame comprises a plurality of struts bonded to the guidewire at a first end, and the struts expand radially outward at a second end. The frame may comprise an inflation seal for providing better contact with the vascular walls. The construction and use of expansion means and associated filter mesh have been thoroughly discussed in earlier applications including Barbut et al., U.S. application Ser. No. 08/533,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr. 30, 1996, Barbut et al., U.S. application Ser. No. 08/645,762, filed May 14, 1996, and, Barbut et al., U.S. Pat. No. 5,662,671, and the contents of each of these prior applications are expressly incorporated herein by reference.
In still another embodiment, the guiding catheter includes an infusion port proximal to the occlusion balloon. The port communicates with an infusion lumen in the catheter and is adapted for infusion of fluid or pharmaceutical agents. Using the infusion port, the dosage of pharmaceutical agent required to achieve local effect can be reduced compared to administration by systemic route. Side effects, e.g., hemorrhage associated with systemic administration of t-PA, can also be minimized. In certain embodiments, the angioplasty catheter may include an infusion port proximal to the angioplasty balloon and a perfusion port distal to the balloon. The infusion and perfusion port communicate, respectively, with an infusion and perfusion lumen included in the angioplasty catheter. The infusion port is adapted for aspiration of fluid, blood, air, or vascular debris.
The methods of the present invention include protecting a patient from embolization during an endovascular procedure to remove plaque and/or thrombi from the coronary artery, aorta, common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery, and all other arteries carrying oxygenated blood. The methods also include prevention of distal embolization during an endovascular procedure to remove thrombi and/or foreign bodies in the venous circulation, including the superior vena cava, inferior vena cava, external and internal jugular veins, brachiocephalic vein, pulmonary artery, subclavian vein, brachial vein, axillary vein, iliac vein, renal vein, femoral vein, profunda femoris vein, great saphenous vein, portal vein, splenic vein, hepatic vein, and azygous vein.
In a first method of using the filter flush system, the distal end of the guidewire, having the filter in a collapsed state, is inserted through an artery or vein. The filter and the distal region of the guidewire are positioned in the vessel beyond a region of interest, followed by expansion of the filter. The guiding catheter is inserted over the guidewire, and the occlusion balloon is positioned proximal to the region of interest. The distal region of an atherectomy, stent-deployment, or angioplasty catheter is inserted over the guidewire, where the guidewire is carried within the lumen of the guiding catheter, and advanced to the region of interest. The occlusion balloon is then expanded to isolate blood flow in the vessel while the endovascular catheter removes or otherwise treats the stenotic lesion in the vascular lumen. The catheter may then be withdrawn or left in place, and fluid or blood is infused through the lumen of the guiding catheter to flush embolic debris into the expanded filter. In certain embodiments, the fluid is directed as a jet toward the atheroma for the purpose of blasting the atheroma from the wall of the vessel and thereafter into the filter. The steps of inserting the endovascular catheter and infusing fluid to flush embolic debris may be repeated until an adequate lumenal diameter is established. The filter is then collapsed and removed, together with the captured embolic debris, from the vessel by withdrawing the guidewire. The guiding catheter is withdrawn after the occlusion balloon is deflated.
In another method, after the expanded filter and the guiding catheter are positioned, respectively, in a vessel distal to and proximal from the region of interest, the angioplasty balloon carried by the angioplasty catheter is inflated to dilate the stenotic vascular lumen. Blood, fluid, air, and/or embolic debris present between the occlusion and angioplasty balloon may be aspirated. Alternatively, the occlusion balloon may be deflated during the inflation of the angioplasty balloon to allow blood to be aspirated from the proximal port and passed to the perfusion port distal to the angioplasty balloon, thereby maintaining perfusion to the distal organs during angioplasty.
It will be understood that there are several advantages in using the devices and methods disclosed herein for capturing and removing embolic debris during endovascular procedures. For example, the filter flush system (1) is particularly suited for temporary filtration of blood in any vessel to entrap embolic debris, thereby minimizing neurologic, cognitive, and cardiac complications associated with distal embolization, (2) can withstand high arterial blood flow for an extended time, (3) includes a mesh that is porous enough to allow adequate blood flow in a blood vessel while capturing mobile emboli, (4) is adapted to accommodate an endovascular catheter with or without imaging device, (5) may remove mobile plaque in a vessel by flushing through the guiding catheter, (6) provides means to maintain perfusion to distal organs during endovascular procedures, (7) provide means to administer pharmaceutical agents, e.g., tissue plasminogen activator or nitroglycerin, locally to the region of interest, thereby minimizing side effects associated with systemic administration, and (8) can be used in adult and pediatric patients.